1. Field of the Invention
This invention relates to an abrasive tape to be used for polishing a magnetic head, a floppy disk head, a hard disk head, or the like. This invention particularly relates to an abrasive tape to be used for finish polishing a rough-polished surface of a magnetic head, a floppy disk head, a hard disk head, or the like.
2. Description of the Prior Art
Video or high-grade audio magnetic heads are made by being polished with abrasive tapes. The abrasive tape comprises a flexible substrate, and an abrasive layer overlaid on the flexible substrate. In order for the abrasive layer to be provided, an abrasive composition containing abrasive grains, a binder, additives, and the like, is applied onto the flexible substrate and dried.
In general, when the surface of a magnetic head, or the like, is to be polished with the abrasive tape, two reels are positioned with the magnetic head, or the like, intervening therebetween. The abrasive tape is moved between the two reels while it is in contact with the surface to be polished. The abrasive tape is flexible and can snugly fit to a curved surface. Therefore, the abrasive tape is more suitable for the polishing of the curved surface of the magnetic head, or the like, than grinding wheels. Also, the abrasive tape can achieve scratch-free, accurate polishing of the surface to be polished, and is therefore indispensable to finish polishing of a rough-polished surface.
As is well known, polishing processes wherein the abrasive tape is used are carried out for the purposes of, for example, shaping the tip of a magnetic head into a desired form, eliminating the chipping of a magnetic head, and polishing the surface of a magnetic head to a smooth finish. In order for the polishing process to be satisfactorily achieved, it is required that the polishing performance be increased, thereby to shorten the time required for the polishing, and that the smoothness of the polished surface be increased. Abrasive tapes for satisfying such requirements have heretofore been proposed. For example, Japanese Patent Publication No. 62(1987)-10782 discloses an abrasive tape provided with an abrasive layer, which is constituted of a mixture of two kinds of abrasive grains, such that both the polishing performance and the smoothness of the polished surface may be improved.
Recently, rapid advances have been made in the performance of video heads, and a combination head has been developed like that in C Movie NV-M50 supplied by Matsushita Electric Industrial Co., Ltd. FIGS. 6 and 7 are a plan view and a front schematic view showing a combination head. As illustrated in FIGS. 6 and 7, the combination head comprises a combination of an audio head C and a laminated type of amorphous head (video head) D, which are secured to a single head base plate E. The audio head C is composed of a glass material part "a" and a ferrite material part "b." The video head D is composed of a glass material part "c," an amorphous metal material part "d," and a ceramic material part "e." When a finish polishing process is carried out on the combination head, it is necessary that the audio head C and the video head D are polished so as to have the same heights of the polished surfaces, and that the polished surfaces are highly smooth. If the heights of the polished surfaces are not equal to each other, space loss will occur during the magnetic recording and reproducing operations, so that the magnetic recording and reproducing characteristics will be deteriorated.
The abrasive tape disclosed in Japanese Patent Publication No. 62(1987)-10782 has a low polishing performance with respect to the video head of the combination head described above. Therefore, the disclosed abrasive tape has drawbacks in that the audio head and the video head cannot be polished so as to have the same height.